There are existing atomizer designs for the applications described above, the designs typically providing a spray that is dynamically controlled to vary air humidity level. Usually an array of nozzles is mounted within a duct or other area and the required humidification supply is varied by adjusting air and water pressures to suit the desired bulk vaporization rate. The existing nozzles suffer from a number of shortcomings, such as high air consumption, the collection of large droplets on external components of the assembly, relatively high cost, difficulty in providing a limited or controlled droplet size distribution, and high noise levels due to high air consumption.
Many current nozzle designs are configured Dr optimized for only one flow condition or the operating range is very limited for achieving consistent, unchanged droplet size. Also, many of the present designs that use air atomization are designed with one or more impactor plates that produce fine spray (typically less that 50 μm mean size) but the mounting for each plate interferes with the spray and often results in a fraction of the spray comprising course droplets resulting from an accumulation of liquid on the impactor-mounting components. Another problem associated with prior art nozzles, as indicated above, is the noise level produced by the nozzles since they are used in commercial building air conditioning. The high noise level of the prior art nozzles is usually attributed to high air consumption—thus a low air consumption is desirable.
U.S. Pat. No. 4,483,482 of Nov. 20, 1984 is representative of prior art designs. It utilizes a convergent/divergent tube-path to accelerate gaseous fluid into an annular mixing chamber where the fluid mixes with liquid entering downstream of the gaseous fluid inlet. The mixed fluid and liquid flow along an annular path towards the nozzle exit from which the fluid and liquid are sprayed in a fan-like pattern from the flared end of the nozzle. This nozzle suffers from all of the drawbacks enumerated hereinabove.